From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, ji_ang , Anton Vorontsov , Andrew Morton , Linus Torvalds Subject: [PATCH 3.17 02/47] mm/vmpressure.c: fix race in vmpressure_work_fn() Date: Sun, 14 Dec 2014 12:20:37 -0800 Message-Id: <20141214201818.625367563@linuxfoundation.org> In-Reply-To: <20141214201818.552715149@linuxfoundation.org> References: <20141214201818.552715149@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrew Morton commit 91b57191cfd152c02ded0745250167d0263084f8 upstream. In some android devices, there will be a "divide by zero" exception. vmpr->scanned could be zero before spin_lock(&vmpr->sr_lock). Addresses https://bugzilla.kernel.org/show_bug.cgi?id=88051 [akpm@linux-foundation.org: neaten] Reported-by: ji_ang Cc: Anton Vorontsov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/vmpressure.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/mm/vmpressure.c +++ b/mm/vmpressure.c @@ -165,6 +165,7 @@ static void vmpressure_work_fn(struct wo unsigned long scanned; unsigned long reclaimed; + spin_lock(&vmpr->sr_lock); /* * Several contexts might be calling vmpressure(), so it is * possible that the work was rescheduled again before the old @@ -173,11 +174,12 @@ static void vmpressure_work_fn(struct wo * here. No need for any locks here since we don't care if * vmpr->reclaimed is in sync. */ - if (!vmpr->scanned) + scanned = vmpr->scanned; + if (!scanned) { + spin_unlock(&vmpr->sr_lock); return; + } - spin_lock(&vmpr->sr_lock); - scanned = vmpr->scanned; reclaimed = vmpr->reclaimed; vmpr->scanned = 0; vmpr->reclaimed = 0;